A Purge Valve For On Board Fuel Vapor Recovery Systems is disclosed in U.S. Pat. No. 4,944,276. That purge valve comprises a solenoid-controlled valve and a regulator valve that are in series between the purge valve's inlet and outlet ports. The regulator valve makes the response of the purge valve to electrical signals acting upon the solenoid-controlled valve relatively insensitive to variations in the intensity of intake manifold vacuum at the outlet port over a certain range of magnitude of vacuum. Even when the purge valve includes this regulating function, difficulties are encountered in accomplishing controlled purging of the canister at engine idle when the manifold vacuum is high and the flow of combustible mixture into the engine cylinders is relatively low. The present invention is directed to a solution to this problem and provides a new and improved regulated canister purge solenoid valve which is capable of providing improved purge control at engine idle.
The improved purge valve of the present invention accomplishes this result without the necessity of major modifications to the previously known purge valve, and therefore provides a very significant functional benefit in a quite cost-effective manner. It is believed that the valve of the invention will be capable of assisting evaporative emission control systems of future automotive vehicles in attaining compliance with stricter government-promulgated evaporative emission standards.